Multiple choice

A boat covers a certain distance downstream in 1 hour, while it comes back in $1\frac{1}{2}$ hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?

  1. 12 kmph

  2. 13 kmph

  3. 14 kmph

  4. 15 kmph

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let boat speed be B and stream speed be 3. Downstream speed = B+3, Upstream speed = B-3. Distance = (B+3)*1 = (B-3)*1.5. B+3 = 1.5B - 4.5. 0.5B = 7.5. B = 15 kmph.

AI explanation

Let the speed of the boat in still water be B and the distance be D; since distance is constant, downstream speed multiplied by 1 hour equals upstream speed multiplied by 1.5 hours. This simplifies to (B + 3) = 1.5(B - 3), which expands to B + 3 = 1.5B - 4.5. Solving this equation yields 0.5B = 7.5, so the speed of the boat in still water is 15 kmph.

Keep practicing — related questions